It's a Brother Thing
by mediwitch3
Summary: Sam's got a sensitive bottom and it's his birthday. WARNINGS: Underage, spanking, weecest, incest, frottage.


The first time it happens, Dean doesn't think much of it. Sam skitters away like a spooked horse, the yelp on his lips sounding indignant and just a little bit desperate, so Dean does what any normal person would do—laughs it off.

"Aw, does Sammy have a sensitive ass?" he simpers, batting his eyelashes obnoxiously at his brother. Sam just scowls and marches off in a huff. A few moments later, Dean hears a door slam, jarring an eye roll out of him. Whatever. Sam can be a bitch if he wants to, Dean's getting pizza rolls.

It becomes a pattern, just another way for Dean to push Sam's buttons. Sam hates it, gets nervous and angry when Dean taps is ass gently on his way past him to the fridge, will throw a fight if they're sparring and Dean reaches around to smack him. Dean's not sure where this kind of sensitivity comes from, but Sam looks at him guiltily and resentfully whenever he asks, so Dean doesn't.

Dean's twenty when Sam turns sixteen, all broad shoulders and girly hair that falls in his face when he leans over too far. Sam's been shooting up these past few months, filling out in all the right places, face changing from that of a boy to that of a man, baby fat melting away to leave sharp cheek bones and a strong jaw.

For all Sam has changed, though, Dean knows he hasn't. He's still a broody little fucker, still smart and gagging for more books more books. When he smiles, the dimples still carve themselves into his cheeks, and he still pouts like the four-year-old Dean swears he was yesterday. Above all else, however, is Sam's ass. Still just as sensitive and irritation inducing as it was when he was twelve.

So, naturally, Dean wakes him on his birthday with a smack on the ass. Sam jerks awake, looking startled and half-asleep, glancing around the room with a muttered _wuzgoinon?_. Dean grins, patting him gently twice, which only seems to startle Sam more.

"Up and at 'em, sunshine, it's your birthday!" Dean beams down at him, "Come on, come on! I made pancakes, bitch, they're getting cold!"

Sam grumbles, throwing back the covers and swinging his feet out of the bed. They hit the floor with a thump, and he doesn't bother putting on pants as he brushes past Dean on his way out the door. Dean follows him down the stairs, contemplating his next move—and if his next move _happens_ to involve Sam's ass, that's not gay or incestuous. It's a brother thing.

Dean pats Sam's ass as he moves past him into the kitchen to get the food, and again as Sam brings his empty plate to the sink. Sam's scowl deepens each time, and Dean's grin only widens in response. The glee seeps out quickly, though, when Sam plunks himself in Dean's lap. Dean's still sitting at the table, reaching for another forkful of pancakes, and Sam just sits down. In Dean's lap. What.

"Uh, Sam," Dean starts nervously, hands fluttering as he doesn't know what to do with them, "what are you doing?"

Sam shrugs, "I figured you'd want more contact with my ass, since, you know, you keep hitting it."

Dean splutters, really not sure how the tables turned on him so quickly, "Sam, you're not a kid anymore, you can't just sit in my lap."

"It's my birthday," Sam says haughtily, like he knows Dean can't deny him on a good day, let alone his birthday, "I can do what I want."

Sam flings one leg over Dean's waist, leaving Dean startled with a lapful of baby-brother. Sam leans forward, putting his mouth next to Dean's ear as he grinds down gently.

"Don't tell me you don't want this too?" Sam asks, with what probably only Dean can read as nervousness, "You seem to have this... Fascination with touching my ass."

"You like it," Dean responds automatically, almost regretting it as Sam grinds just a little bit harder.

"You're right," Sam smirks, nerves bleeding away, "I do."

Sam starts grinding down in earnest now, his face flushing gently as he pants against his brother's ear. Dean doesn't quite know what to do—except it's Sammy, and in the back of his mind he's always known it'd come to this.

So what can he do but play along?

"Sam," Dean huffs—because he's getting hard himself, "Get off."

"What?" Sam leans back, looking into Dean's face confusedly. Dean rolls his eyes.

"Off. I want you across my lap—now, please," Dean uses his command voice, the one that brooks no argument. Sam does as he's told, long legs settling against the chair and on the floor, ass in the air. Dean strokes a hand over one cheek, contemplating his next move as Sam tenses over him in anticipation. If he does this, there's no going back—if he doesn't, though... He doesn't want to see Sam's reaction to that. They've reached a point where they can only go forward, even if forward isn't the normally traveled path. Dean finds himself surprisingly okay with this, and it's that thought that brings his hand back, only to swing down and land with a muffled _smack_ against the boxers Sam's wearing.

"You know this is wrong, right, Sam?" Dean asks, bringing his hand down again, Sam inching forward on his lap, his face buried in his brother's thigh, "That you want this? We're brothers, Sam. And you get off on me spanking you?"

Sam just groans, his face hot where it presses against Dean's leg. His hips are grinding against Dean's other thigh, his back muscles twitching with the simple effort of staying so still. Dean decides he's had enough of this 'clothing' business, so he shoves his hand up Sam's shirt to caress the skin there.

"Pants. Off," Dean grunts, watching as Sam hastens to do as he's told, boxers hitting the floor and pooling around Sam's knees where they're bent. He leans back over, this time staring up at Dean through hooded eyelids. Dean brings his hand up, bringing it back down harder than before across his little brother's bottom. The _smack_ of it rings through the room followed closely by a loud groan. Sam squeezes his eyes shut, grinding his hips down against his brother's thigh, his cock hard and leaking.

Sam whines as Dean's hand comes down again, the skin of his ass red and sore. He shoves his face forward, into Dean's crotch, biting his lip as the obscene bulge of Dean's dick pushes against his face. He opens his mouth the next time Dean hand hits him, a breath forcing its way out of his lungs.

Dean's groaning now, too. Sam's mouth is pressing against his dick through his jeans and he's grinding his own cock against Dean's leg and it's a lot. Too much. Dean wraps an arm around Sam's waist, gently pulling him off his lap. Sam sits up obligingly, scrambling hastily into Dean's lap again to straddle his older brother.

After that Dean doesn't honestly remember much. There's a lot of grinding and it's hot and they're panting into each other's mouths and Sam comes all over his favorite shirt and Dean can't take it anymore and he ruins his pants. Sam collapses back into his lap, not mindful of the sticky ejaculate all over their tshirts. He rests his forehead against Dean's shoulder, breathing heavily.

Dean slumps heavily against the chair, "We're okay, right Sam?"

"Yeah, Dean," Sam grunts, obviously half-asleep, smile curling against Dean's neck, "We're fine."

Dean decides not to worry about too much, instead lifting his gangly brother and stumbling up the stairs where he changes them both and flops next to Sam on the bed. It's just a Sam and Dean thing.


End file.
